LATEX is a macro-package for TEX which has many preset environments
where much of the setting up that TEX users have to do explicitly is done
for you. An environment has the form

\begin{environment name}

.

\end{environment name}

LATEX also has commands which affect the formatting of the document.
Their arguments are given in braces. For example,

\textit{This is much more important} than this.

produces as output This is much more important than this.

The related \itshape command doesn't take an argument. It affects
all the subsequent text in the environment where it's used.

LATEX tries to enforce the idea that the visual appearance of
the document (use of fonts, indentation, etc) should derive from the
logical structure of the document (i.e. rather than manually
putting the section titles into bold, you should let the \section
command do it). Resisting this philosophy can lead to
extra (usually unnecessary) work.

LATEX is expandable. Many macros can be loaded in to provide added
features. You can also create your own commands and environments. Commands
can take arguments that modify their action

Some commands have a *-form, a variant on the standard command
that you get by adding a * to the command name.